The next field of Souliman’s military enterprise was Persia, where the Shah, by the defection of an Ottoman official, had recovered some of the territory taken by Selim. Souliman, appearing with a large force, received the submission of many of the Shah’s vassals, and, after a long march to the East, during which his cannon had to be abandoned, entered the ancient capital of the Khalifate, Bagdad, in 1535. But several other campaigns were required to establish definite possession of the country. Finally, after many victories, peace was signed at Amasia, on the 29th of May, 1555, a step which implied that the Sunnite Turks acknowledged the legitimacy of a Shiite monarchy. In the mountains of Armenia and Kurdistan the extension of Ottoman power encountered serious obstacles. Native chieftains and princes followed their own caprices and their own interests in changing their allegiance to Shah or Sultan. There was constant guerrilla warfare, without any notable advantage to Turkish arms. In the southern regions at the confluence of the Tigris and the Euphrates, the Ottoman power was firmly established; Turkish vessels were to be seen now in the Red Sea and the Persian Gulf. Aden was occupied and the control of Yemen made effective. But the chief effort of Souliman was directed against the King of Hungary and the Emperor Charles V. A curious and novel development of European diplomacy was seen, when Francis I, the French King, appealed to the Sultan in his difficulties, after his defeat at the hands of Charles in Italy. Souliman sent a gracious message assuring the imprisoned monarch of his support, and spoke of his own throne as the refuge of the world; “night and day,” he added, “our horse is saddled and our sword girded.” In 1526 the Sultan marched from his capital to give battle to Charles, the “hated head of the infidels,” with an army of 100,000 men and 300 cannon. There was a great battle with the Hungarian troops at Mohacs (August 28, 1526). After a hot engagement of two hours, the Christians left on the field 20,000 foot and 400 horse, and of the prisoners 400 were put to death.